Mattias J Curlin

INTRO

My name is Tai Curlin and I am a senior at Sunset High School in Beaverton, Oregon. I enjoy cross-country running, and playing chess and am interested in French language and bioengineering.

This fall, I did a series of environmental toxicology experiments looking at the possible harmful effects of mobile phones, and a few materials that are commonly found in my environment.

MY PROJECT

Experiment 1 - Many people wonder if cell phone exposure is bad for you. In this project I decided to look at whether whether cell phone exposure could cause a harmful effect on bacterial growth in culture. To do this I set up several parallel bacterial cultures in liquid medium in an incubator at 37 degrees Celcius for two hours. During the incubation, I exposed the samples to an active cell phone at close range for varying periods of time. I was expecting to see either nothing, or maybe a harmful effect on bacterial growth at longer exposure times….

Abstract

Introduction: Evidence for a health effect of lower-energy non-ionizing electromagnetic radiation (NIR) is discordant. The dramatic rise in mobile phone use over the past two decades has prompted significant concern about possible health effects of exposure to emfs generated by phones. To explore the possible effect of EMF toxicity, we examined the effect of mobile phone exposure on bacterial cell growth in culture.

Methods: We exposed growth-phase bacteria in solution from a commercial kit (SOS-ChromoTestTM) to non-ionizing radiation by placing samples in close proximity to an iPhone 13 mini in active use. This experiment was conducted in an incubator at 37 °C. Bacterial culture samples were exposed for varying lengths of time ranging between 15 and 120 minutes and compared with a control group without exposure after 2 hours total incubation time. Growth was assessed by measurement of optical density at 600nm using a 96-well microplate spectrophotometer.

Results: We observed a significant increase in bacterial cell growth with short term with 15-minute exposure to mobile phone radiation (p<0.001), and a smaller affect with 60-minute exposure (p<0.001), but no effect with exposure with 90- and 120-minute exposure (p>0.2).

Conclusions: In this study we were not able to exclude an effect of mobile phone radiation exposure on the growth of bacteria in culture. In our setting, a significant positive effect on bacterial growth was observed for short-duration exposure, while this effect was lost at longer durations. The mechanisms for this effect are unclear.

Background

Background: There is considerable evidence for the harmful effects of ionizing radiation on human health including various forms of tissue injury such as skin breakdown, cataract formation, sterility, radiation sickness and death. The mechanisms by which non-ionizing radiation might have adverse effects in biological systems are more limited and are thought to include increased temperature as well as oxidative stress. 26371078 However, the evidence for a health effect of lower-energy non-ionizing electromagnetic radiation (NIR) is less clear and is the subject of considerable debate (1-5).

Mobile telephone usage began in the late 1970s, and became highly prevalent by 2000 with the wide availability of affordable compact devices. Between 2019 and 2024 the average time spent on a mobile device increased form 3 hours and 45 minutes to 4 hours and 49 minutes. It is now estimated that there are more cellphones than people. These trends have raised concerns about the possible health effects of NIR associated with cellphone use. Here also, scientific research about this topic has yielded inconsistent reports and is generally inconclusive (6-10).

Several factors have impeded progress including lack of consensus on appropriate research designs, lack of data on long-term effects, and confounding factors such as differences in study populations. Another important confounding factor is that radiation exposure varies significantly with various devices, modes of operation (for example telephone call, downloading content) and usage patterns (for example use of headphones versus use of speaker phone with device in close proximity to the ear). In order to explore the possibility of testing for potential harmful effects of a current model mobile telephone radiation in a simple biological system, we examined the effect of mobile phone exposure of varying duration on bacterial cell growth in vitro.

Methods Schematic

Figure 1. Experimental approach Bacterial cultures in solution, exposed to cell phones for various durations during incubation. After the incuabtion, the samples are aliquoted onto a 96-well microplate, and read in a mircoplate spectrophotometer.

Methods

Bacterial cell growth system: To assess toxicity we used the SOS-ChromoTestTM kit (Environmental Bio-detection Products Inc., Mississauga, Ontario, Canada) according to manufacturer directions as described below (and see Supplementary Material).

Mobile phone exposure protocol: Briefly, using aseptic technique, kit culture bacteria were inoculated in 40 ml of growth medium (supplied in kit) in a sterile a 50 mL falcon conical tube, inverted several times and incubated at 37 °C overnight. On the day of the assay, bacterial culture optical density was measured in a spectrophotometer at 600 nm (Genesys 30, Thermo Fisher Scientific, Walton MA), and diluted to an OD of 0.15 using additional sterile growth medium. Using aseptic technique, 1.4 ml aliquots of diluted bacterial culture were placed in 5 separate sterile 1.5 ml Eppendorf tubes. In a walk-in incubator at 37 °C, tubes were placed in a rack immediately above mobile phone, at a distance of 2 cm from the device. At T = 0’, 15’, 60’, 90’ and 120’, corresponding sample tubes were removed to a distant location within the incubator (approximately three meters) within an aluminum foil faraday cage. Incubation was performed with room lights off. Following completion of incubation, samples were aliquoted into a 96-well plate with seven replicates per exposure sample and one negative control each, and read on a microplate reader (BioTek Epoch Microplate Spectrophotometer, Agilent Technologies, Santa Clara, CA USA) at 600 nm and 420 nm.

Mobile phone: Radiation exposure was performed using an iPhone 13 mini (Apple Corporation, Cupertino, California). During the experiments, the device was receiving a call and simultaneously downloading content in cellular mode, with Wi-Fi and Bluetooth functions turned off. Ambient radiation was measured during the incubation at the exposure location and within the Faraday cage with an electromagnetic field meter (Electrosmog Meter ED88TPlus2, Cornet Microsystems, Santa Clara CA).

Data Analysis: Optical density data were retrieved from the plate reader in excel format and imported into R studio for analysis (R version 4.3.1, RStudio version 2023.06 2+561). Exposure groups were plotted showing bacterial growth (optical density 600 nm) versus dilution. Dilution groups were compared using the T test.

Results

Results Ambient Conditions: the temperature of the incubator was recorded at 37 °C. Electromagnetic radiation near the phone peaked at, but hovered between blank and blank. Measured radiation inside the faraday cage was negligible.

Bacterial growth vs mobile phone exposure: Immediately after incubation, OD value for samples exposed at 15 minutes and 60 minutes were significantly higher than negative control (no exposure) (P<0.001). However, samples exposed for 90 minutes and 120 minutes were not significantly different than negative control (p>0.2) (Figure 1).

Figure 1. Bacterial Growth vs Mobile Phone exposure time. Shown are optical density values for bacterial samples following two hours of incubation at at 37 °C while exposed to mobile phone radiation for 0’, 15’, 60’, 90’, 120’ (blue symbols). Plate negative controls are represented in grey, and kit positive control containing bacteria exposed to 4-nitroquinoline-1-oxide is represented in red. A dose-response effect of radiation exposure is noted.

Discussion

Discussion: In this study we sought to evaluate the effect of mobile phone exposure at variance durations on bacterial cell growth in solution. The main observation was that short-duration exposures (on the order of 15 minutes) appeared to increase bacterial growth. However, exposure at 120 minutes showed no difference with control sample (no exposure). There was a clear dose response curve for times between 15 and 120 minutes.

The findings of this experiment were unexpected. We expected either no effect (null hypothesis) or a detrimental effect on bacterial growth with increasing mobile phone exposure due to harmful effects of radiation exposure. While it is clear that proximity to the mobile phone has an impact on bacterial growth, there appear to be two opposing effects. The first affect seems to occur during brief exposures and promotes bacterial growth. However, although the 120-minute exposure sample should have had this same benefit, the longer exposure time appears to have reversed the beneficial effect of short-duration exposure.

Explanations for our observations are unclear. Heat produced by the mobile phone could affect bacterial growth and be one explanation for the increased growth rate in the 15-minute sample. However, this is not entirely satisfactory as the samples were exposed to ambient temperatures within the incubator. In addition, samples with longer exposure also should have had an early growth boost. Therefore, one must suppose that excess heat also has a negative effect at later times in samples with prolonged exposure. A second possible explanation for the observed growth effect is that some agitation of the tubes during displacement caused different growth kinetics on a sample-by-sample basis. Lastly, electromagnetic radiation itself could cause could be the cause of complex growth dynamics in ways that remain to be explored. In future experiments we plan to control for additional possible confounding variables, increase the number of time intervals, and add assays to detect the effect of gene toxicity.

Conclusions

Conclusion: In this study we were not able to exclude an effect of mobile phone radiation exposure on the growth of bacteria in culture. In our setting, a significant positive effect on bacterial growth was observed for short-duration exposure, while this effect was lost at longer durations. The mechanisms for this effect are unclear.

References

References

1. Belpomme D, Hardell L, Belyaev I, Burgio E, Carpenter DO. Thermal and non-thermal health effects of low intensity non-ionizing radiation: An international perspective. Environ Pollut. 2018 Nov;242(Pt A):643-658. doi: 10.1016/j.envpol.2018.07.019. Epub 2018 Jul 6. PMID: 30025338.
2. Calvente I, Fernandez MF, Villalba J, Olea N, Nuñez MI. Exposure to electromagnetic fields (non-ionizing radiation) and its relationship with childhood leukemia: a systematic review. Sci Total Environ. 2010 Jul 15;408(16):3062-9. doi: 10.1016/j.scitotenv.2010.03.039. Epub 2010 May 7. PMID: 20451240.
3. Pinto R, Ardoino L, Giardullo P, Villani P, Marino C. A Systematic Review on the In Vivo Studies on Radiofrequency (100 kHz-300 GHz) Electromagnetic Field Exposure and Co-Carcinogenesis. Int J Environ Res Public Health. 2024 Aug 2;21(8):1020. doi: 10.3390/ijerph21081020. PMID: 39200630; PMCID: PMC11354106.
4. Karipidis K, Baaken D, Loney T, Blettner M, Brzozek C, Elwood M, Narh C, Orsini N, Röösli M, Paulo MS, Lagorio S. The effect of exposure to radiofrequency fields on cancer risk in the general and working population: A systematic review of human observational studies - Part I: Most researched outcomes. Environ Int. 2024 Sep;191:108983. doi: 10.1016/j.envint.2024.108983. Epub 2024 Aug 30. PMID: 39241333.
5. Miah T, Kamat D. Current Understanding of the Health Effects of Electromagnetic Fields. Pediatr Ann. 2017 Apr 1;46(4):e172-e174. doi: 10.3928/19382359-20170316-01. PMID: 28414399.
6. Howarth, Josh. “Time Spent Using Smartphones (2024 Statistics).” Exploding Topics, Exploding Topexploding topicsics, 4 June 2024, explodingtopics.com/blog/smartphone-usage-stats.
7. Felix Richter. “Charted: There Are More Mobile Phones than People in the World.” World Economic Forum, 2023, www.weforum.org/stories/2023/04/charted-there-are-more-phones-than-people-in-the-world/.
8. Rabiei M, Masoumi SJ, Mortazavi SMJ, Nematolahi S, Haghani M. Mobile Cellular Data and Wi-Fi Use Are Not Associated with Adverse Health Effects. J Biomed Phys Eng. 2023 Dec 1;13(6):497-502. doi: 10.31661/jbpe.v0i0.2206-1511. PMID: 38148957; PMCID: PMC10749419.
9. Karipidis K, Baaken D, Loney T, Blettner M, Brzozek C, Elwood M, Narh C, Orsini N, Röösli M, Paulo MS, Lagorio S. The effect of exposure to radiofrequency fields on cancer risk in the general and working population: A systematic review of human observational studies - Part I: Most researched outcomes. Environ Int. 2024 Sep;191:108983. doi: 10.1016/j.envint.2024.108983. Epub 2024 Aug 30. PMID: 39241333.
10. Morgan LL, Miller AB, Sasco A, Davis DL. Mobile phone radiation causes brain tumors and should be classified as a probable human carcinogen (2A) (review). Int J Oncol. 2015 May;46(5):1865-71. doi: 10.3892/ijo.2015.2908. Epub 2015 Feb 25. PMID: 25738972.

Commentary - I was not really expecting this interesting result. I am still thinking about why this happened (the cell phone seemed to help bacterial growth, but only if exposed for a short time). I am planning more experiments to eliminate some possible confounding variables, like agitation of the sample during removal to the Faraday cage, and short-term temperature effects. TBC…

Experiment 2 - In another experiment, I exposed the bacteria to some substances that people worry might be toxic. The three things I chose were charred red meat (common in our diets), the rubber infill in sport turf fields (which is basically ground up tires), and dust from railroad ties which have been treated with creosote (which sometimes show up in gardens and playgrounds).